John Calvin Commentary 2 Timothy 2:5

"And if also a man contend in the games, he is not crowded, except he have contended lawfully." — 2 Timothy 2:5 (ASV)

And if anyone strive He now speaks of perseverance, so that no one may think that he has done enough when he has been engaged in one or two conflicts. He borrows a comparison from wrestlers, not one of whom obtains the prize until he has been victorious in the end. Thus he says:

In a race all run, but one obtains the prize;
run so that you may obtain. (1 Corinthians 9:24).

If anyone, therefore, wearied by the conflict, immediately withdraws from the arena to enjoy rest, he will be condemned for idleness instead of being crowned. Thus, because Christ wishes us to strive during our whole life, the one who gives way in the middle of the course deprives himself of honor, even though he may have begun valiantly. To strive lawfully is to pursue the contest in such a manner and to such an extent as the law requires, so that no one may stop before the appointed time.